Starches and sugars in food that are a source of energy for the body. Carbohydrates are composed of carbon, oxygen, and hydrogen. They include glucose, sugars, starches, dextrins, and celluloses from plants and glucose, glycogen, and lactose from animals. The simple sugars, glucose, galactose, and fructose, are the end products of carbohydrate digestion, and as such, are absorbed into the bloodstream and used as a basic source of energy.